1. Field of the Invention
The present invention relates to an upper frame for a construction machine such as a hydraulic shovel, and more particularly to an upper frame provided with a side deck on which a cabin is loaded.
2. Description of the Background Art
The background art of the invention will be explained with reference to a hydraulic shovel shown in FIG. 8 as an example.
The hydraulic shovel comprises a crawler-type lower propelling body 1 and an upper slewing body 2 which is loaded on the lower propelling body 1 slewably about an axis perpendicular to the ground. The upper slewing body 2 includes an upper frame 3 as a base thereof, on which various devices including a cabin 4 are loaded. A working attachment 5 is mounted on a front part of the upper frame 3 and on the right side of the cabin 4, and a counterweight 6 is mounted on a rear end of the upper frame 3.
In the specification, the cabin 4 is located on the left-front part, and “left and right directions” (a lateral direction), and “front and rear directions” (a longitudinal direction) are defined with respect to the position of the cabin 4.
FIGS. 9 through 13 show a structure of the upper frame 3.
The upper frame 3 is constituted of a center section A positioned at a center of the upper frame 3 in the width direction of the hydraulic shovel, and left and right side decks B, C formed on left and right ends of the center section A so as to protrude outwardly from the center section A. The working attachment 5 and the counterweight 6 are attached to a front part and a rear end of the center section A, respectively. The cabin 4 is loaded on the left side deck B, and various devices such as an unillustrated tank are loaded on the right side deck C.
The center section A has a bottom plate 7 to which an unillustrated swing bearing is mounted, and a pair of left and right vertical plates 8, 9 formed on the bottom plate 7. The vertical plates 8, 9 vertically rise from left and right ends of the center section A while extending longitudinally.
The left side deck B includes a front beam 10, a rear beam 11, and left and right vertical beams 12, 13, which beams 10, 11, 12 and 13 constitute a frame-shaped body. Furthermore, a connecting member is optionally mounted to an intermediate portion of the body, while only one transverse bar 14 is shown as the connecting member in FIGS. 9 through 12.
The left side deck B has a pair of left and right mount holding members 16, 17 as shown in FIG. 9 and FIG. 10. The mount holding members 16, 17 are disposed at left and right sides of a front end of the left side deck B to hold a front part cabin mount 15 as shown in FIG. 13, respectively. The mount holding members 16, 17 are laterally symmetrical in shape, having the same basic constructions. In view of this, the details of the right mount holding member 17 are exemplarily shown in FIGS. 11 through 13.
Each of the mount holding members 16, 17 integrally includes a horizontal upper plate portion 18 and a rear plate portion 19 extending perpendicularly downward from a rear end of the upper plate portion 18. The right mount holding member 17 is fixed to an inner lateral surface of a corner portion formed by the front beam 10 and the right vertical beam 13 by welding, and the left mount holding member 16 is fixed to an inner lateral surface of a corner portion formed by the front beam 10 and the left vertical beam 12 by welding, respectively. The upper plate portion 18 of each of the mount holding members 16, 17 has a mount insertion hole 20 into which the front part cabin mount 15 is inserted and holds the front part cabin mount 15 inserted into the mount insertion hole 20.
The left and right side portions of the rear beam 11 are provided with similar mount attachment holes 21, 21, respectively, as shown in FIGS. 9 and 10, into which not shown rear cabin mount are inserted respectively to be attached to the rear beam 11.
The above-described structure is disclosed in Japanese Unexamined Patent Publication No. 2000-104284. The publication discloses a technology of attaching a reinforcement member 22 as shown in FIGS. 9 through 13 to at least one of the inner lateral surfaces of the left and right vertical beams 12, 13 to reinforce the left side deck B. FIGS. 9 through 13 show an example in which the reinforcement member 22 is attached to the right vertical beam 13.
The reinforcement member 22 disclosed in the above publication has a cross section integrally including an upper plate portion and a lower plate portion aligned in a vertical direction and a vertical plate portion vertically extending so as to interconnect respective outer ends of the upper plate portion and the lower plate portion, and the upper plate portion and the lower plate portion are joined, for example, by welding to the inner surface of the right vertical beam 13 over the entire length of each of the upper plate portion and the lower plate portion. Besides, the reinforcement member 22 has a rear end to be joined to a front surface of the rear beam 11 and a front end to be joined to the rear plate portion 19 of the right mount holding member 17. The rear end of the reinforcement member 22 is joined to the front surface of the vertical joint plate in the case where a rear portion of the right vertical beam 13 is cut and another beam member is joined to the reinforcement member 22 via a vertical joint plate for convenience of e.g. pipe connection; alternatively, the rear end of the reinforcement member 22 is joined to the front surface of the connecting beam in the case where a connecting beam is bridged between respective longitudinally intermediate portions of the left and right vertical beams 12, 13.
The structure as described above has a problem of a low reinforcement effect at the front end of the reinforcement member 22. In this structure, the front end of the reinforcement member 22 is indirectly joined to the front beam 10 via the mount holding member 17, which forces the mount holding member 17 to serve as a part of a reinforcement member, in other words, forces the mount holding member 17 to constitute an extension of the reinforcement member 22; however, the mount holding member 17 is just designed to support the cabin 4 and not designed to provide such a high reinforcing effect as expected differently from the reinforcement member 22. Why the front end of the reinforcement member 22 is joined to the mount holding member 17 is just that the mount holding member 17 is located on the front end side of the reinforcement member 22. Specifically, the mount holding member 17 has only so a smaller plate thickness than that of the reinforcement member 22 as to have lower strength and rigidity than those of the reinforcement member 22. Hence, the structure, where the mount holding member 17 constitutes a part of a reinforcement member, has only a low reinforcement effect at a front part of the mount holding member 17, which makes the strength and rigidity of the entirety of the left side deck B be insufficient, resulting in the possibility of failure to meet the requirement on ROPS, which is the safety standard of a cabin in case of rollover of a construction machine.